Is it possible to change elevation angles in the Vertical Coverage Diagram?

Question

Micah Price 2018-7-24

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https://ww2.mathworks.cn/matlabcentral/answers/411878-is-it-possible-to-change-elevation-angles-in-the-vertical-coverage-diagram

回答： Honglei Chen 2018-7-24

I have discovered that pattern angles (in the following example from MATLAB) work from -60 degreess to 90 deg, -90 to 60 and obviously -90 to 90. But, the moment you change the angles to -90 to 59 deg, function antresp = antfactor(anpat,patangles,theta) in the radarvcd.m file gets NaNs in the last eleven columns of the 1x674 double. Consequently the remaining functions fail. How come NaNs are being returned and how can I get around this to produce a graph restricted from 0 to 45 deg or -20 to 15 deg?

VCDforSincPatternAntennaExample.m

if true
  pat_angles = linspace(-90,90,361)';
  pat_u = 1.39157/sind(45/2)*sind(pat_angles);
  pat = sinc(pat_u/pi);
  freq = 100e6;
  ant_height = 10;
  rng_fs = 200;
  tilt_ang = 0;
  [vcp,vcpangles] = radarvcd(freq,rng_fs,ant_height,...
  'RangeUnit','km','HeightUnit','m',...
  'AntennaPattern',pat,...
  'PatternAngles',pat_angles,...
  'TiltAngle',tilt_ang,'SurfaceRoughness',1);
end

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Answer 1

Honglei Chen 2018-7-24

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The reason for nan is that when the function computes the vertical response, it needs to access the pattern value out of the specified range. When the value is not available, NaN is returned. Thanks for reporting this.

It would still be a good idea to specify the entire pattern so the computation would have the necessary information. Currently there is no option to return only portion of the region so the best thing to do right now is to extract the needed region. Here is an example

min_ang = 0;
max_ang = 45;
plotidx = (vcpangles>=min_ang) & (vcpangles<=max_ang);
blakechart(vcp(plotidx), vcpangles(plotidx), 200, 600e3, 'RangeUnit','nmi',...
    'HeightUnit','ft')